Q: How much cardio should I do to lose weight?

A: I often hear from people who tell me how hard they are working to get lean and toned, but they just aren't seeing results. Here's the harsh truth: the word "toned" essentially means "muscle," and you can't have tone without it.

I'm not saying cardio workouts are bad by any means. However, in some cases they can sabotage your undying attempts to get that awesome muscle tone and have your body ready for beach season.

Here are a few things to consider when gauging how much cardio you should do, as well as what kind and why.

Type

There are usually two options: long-distance, steady-state cardio, like jogging; or high intensity interval training (HIIT). HIIT can be applied to all sorts of things. It means going fast and slow for intermittent bursts, as with sprints.

This is important to consider, because too much long-distance cardio actually changes your muscle fibers. They go from fast-twitch fibers (which are stronger and bigger), to slow-twitch fibers (which are designed for endurance). This conversion makes the body a lot more efficient when you run long distances; however, your muscles are smaller and weaker, which is a bad thing if you want more muscle tone.

On the other hand, if you are doing HIIT training, you are working at a higher percentage of your max heart rate for shorter durations before you bring your heart rate down and recover. This does a few things. First, because of the higher intensities, your muscles are forced to burn carbohydrates and high energy phosphates to accomplish your quick bursts. Only type 2 fast twitch fibers typically rely on these energy sources. Remember, these are bigger, faster and more powerful muscles. Second, because your fuel source is different than steady-state running and you are forced to activate more muscles due to the explosive nature of HIIT training, your muscles won't adapt by shrinking. If anything, they are going to get bigger and stronger. Think of how a sprinter looks versus a distance runner. Get the point?

HIIT will also put you in "oxygen deficit." Basically, during the workout your body uses more oxygen than it takes in, and you burn a large amount of carbohydrates to fuel your maximal efforts. When the workout concludes, your body has to re-oxygenate, refuel and recover. This takes energy from calories. Specifically, fat calories are burned after an HIIT workout as you recover, a phenomenon known as excess post-oxygen consumption (EPOC), or the after-burn affect. This keeps your valued muscle and burns the fat around it, giving you "tone."

HIIT has proven to be a superior method for maximizing fat loss compared with moderate intensity steady-state training. Despite lower fat burn rates during exercise, fat loss is nevertheless greater over time in those who engage in HIIT versus training in the "fat burning zone"—providing further evidence that 24-hour energy balance is the most important determinant in reducing body fat.

Mode

What equipment are you using to do your cardio? Running, walking outside, treadmill, elliptical, bike, recumbent bike, stair stepper?

The mode of cardio makes a huge difference in terms of proper strength and size development in response to resistance training. Endurance running or walking has been shown to cause significantly more decrements in the development of muscle size than cycling—according to a study that compared cycling with incline walking on a treadmill (a common cardio practice in the bodybuilding community). The study found that cycling was significantly better for achieving hypertrophy (i.e., building muscle) than incline treadmill walking.

Researchers concluded that the differences are likely due to the joint angles and movements required to activate more musculature in cycling than in walking. This leads to the conclusion that doing the stair stepper and sprinting are more efficient because of a range of motion that mimics actual weight-training exercises. It also leaves us wondering: why would anyone bother with a recumbent bike unless they're coming back from an injury?

What about the elliptical? It would be easy to assume that because the joint angles aren't as great, the elliptical may be inferior to biking or stair-stepping. However, a recent study tells us differently. The purpose of the study was to evaluate the contributions of the three main energy pathways during a 30-second elliptical all-out test (EAT) compared with the Wingate all-out test (WAT). The results showed that the elliptical more closely resembles sprinting (running) and weight training in regard to energy system demands than does the bike, although it is important to realize this is during one all-out sprint effort.

So for HIIT training, the elliptical may be superior to the bike. As for steady state cardio, the choice is yours and the two are probably not too far off from each other.

Duration/frequency

How much cardio are you doing and how often are you doing it? If you're reading this because of the title, I assume you're doing quite a bit of cardio, i.e., more than five times a week for 30-plus minutes. There's a fine line to walk here, and multiple factors need to be considered, such as: how often are you doing cardio and what type are you doing?

As I said earlier, too much steady-state cardio changes your muscles. They become smaller and more efficient. Over time, this efficiency leaves you burning fewer calories both during and after your workout, because your overall muscle mass has gone down and your metabolism is slower because of it. More muscle equals higher calorie burn and higher metabolism.

On the other hand, if you are doing too much HIIT cardio, your body may become over-trained. If this happens, you will find it very difficult to recover and continue holding onto muscle mass while burning fat.

When are you doing your cardio? One of the big mistakes I see people making in the gym is doing cardio before resistance training. The problem is that they are working against their bodies' primary order of energy systems, which work more efficiently for a reason.

This means you should do cardio after resistance training. Your body uses up its stored energy during the resistance training and is then primed to burn oxygen and fat for fuel during the cardio session. If you follow this sequence, you can make the most gains and get more "bang for your buck."

Should you do cardio on an empty stomach in the morning? This topic has been debated for years. Some people claim it works wonders for them; others claim it kills their muscle gains in no time.

Both can be true. Here's why:

Protein loss is estimated at 10.4 percent of the total caloric cost of exercise after one hour of moderately intense cycling. This suggests that performing cardiovascular exercise while fasting might not be advisable for those seeking to maximize muscle mass.

Studies have also shown that during moderate to high intensity cardiovascular exercise in a fasted state—and for endurance-trained individuals, regardless of intensity—significantly more fat breaks down than the body can use for fuel. Free fatty acids that are not oxidized ultimately reform as fat cells, nullifying any fat-burning benefits afforded by pre-exercise fasting.

So there you have it. Cardio on an empty stomach is not the best idea. If you want to perform low-intensity walking, that wouldn't be a terrible idea. However, I'm not sure the extra time and work balances out with the low amount of calories you would burn. For the "chemically enhanced" bodybuilder, chances of muscle loss are on the low side, while maximizing fat burn only increases.

How much are you eating? This can make or break your progress. Eat too little and your metabolism slows, you lose muscle and you get closer to overtraining. Eat too much, and your caloric deficit won't be great enough to see visually.

Finally, how often are you lifting weights? This is all over the place nowadays but it's a serious question. Lifting is just as important as cardio training for getting toned and lean. As you know by now, muscle tone = muscle. The more muscle you have, the more calories you burn, the more toned you can become. Keeping and building muscle should be your primary concern when you're trying to get lean or toned.

Recently a friend of mine who I know for a fact does a ton of cardio told me he needed to lose weight and get rid of his gut. In fact, he needed to do just the opposite. His body had become so used to aerobic activity and lighter weights that he had become "skinny fat." He needed to put on muscle.

If you fall in this category, my suggestion is to pick up some heavy weights, dial back the cardio and let your body put on some muscle. If you can put on clean muscle, your body fat percentage will go down, your gut will shrink, and you will be leaner and meaner with a higher metabolism.

Mike Willey
- Mike Willey is the owner of JustFit (Orlando, Florida) and a strength coach at Orangetheory Fitness, which was recognized by 'The New York Times' as "the best one hour workout in the country." He received his Bachelor's in Exercise Science and his Master's in Exercise Physiology from the University of Cen
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